This proposal requests a Population Research Computer System (PRCS) to serve the present as well as the more long-term computer needs of investigators who are Associates of the NICHD-funded Hopkins Population Center (HPC). Recent advances in computer technology offer opportunities to: (1) share online data and specialized software; (2) exploit the powerful new generation of research workstations; and (3) apply new statistical and graphics analysis techniques. The proposed PRCS has three principal components designed to take advantage of these opportunities: (1) migration to the current generation of DOS machines and LAN technology; (2) installation of a new UNIX server and several high-performance graphics workstations; and (3) provision of the interfaces, peripherals, and connectivity equipment that will allow these types of hardware to work seamlessly together. The Hopkins Population Center, established in 1972, currently supports the work of 36 faculty of the Johns Hopkins University (Center Associates) engaged in population-related research in demography, sexual and reproductive health, and reproductive biology. HPC associates have made major contributions to knowledge and, directly or indirectly, to health and social policy formation in adolescent fertility and family structure change in the United States, fertility and child survival in developing countries, stable population theory, indirect estimation of demographic parameters, and male reproductive physiology. Work in these areas, as well as in the newly-important areas of behavior change in relation to STDs and HIV infection, is ongoing. The proposed PRCS will enhance the research productivity and efficiency of HPC investigators, both through its impact on the work of individual researchers and through its facilitation of collaboration among HPC associates.